The goal of this research is to determine whether the systematic application of the monoclonal antibody technology can contribute to the study of lung development. The strategy will be to develop a panel of mouse monoclonal antibodies to antigens expressed on rat lung cells and then use them in an attempt to identify cell surface molecules which are differentially expressed on lung cells as they progress down divergent pathways of development. Four specific aims outline the research: 1. Produce a panel of mouse monoclonal antibodies to fetal rat lung cells. Mice will be immunized with fetal rat lung cell membranes, hybridomas produced by the Kohler-Milstein technique, and the resulting antibodies will be tested for reactivity with fetal rat lung tissue sections. 2. Analyze lungs at different developmental stages for the expression of antigens identified with the antibodies. This will be essentially a selection process for identifying antibodies for further study. 3. Isolate and characterize selected antigens. Antigens expressed differentially on cells of varying types and levels of maturation will be selected for biochemical characterization. 4. Use selected antibodies to identify cell surface molecules important for lung development. Two simple models of early lung development will be established; cell-cell aggregation and mesenchyme-epithelium interaction. Appropriately prepared antibodies selected for reactivity with the antigens previously identified will be used in an attempt to alter these models. Such antigens will be deemed "developmentally important" and singled out for further study. Verification of the utility of monoclonal antibodies in studies of lung development has important health relatedness. It will provide direction for study of many diseases afflicting lung. These include lung neoplasms, inflammatory lung disease, cystic fibrosis, hyaline membrane disease, and emphysema. More knowledge regarding lung cell development and regulation is essential in order to impact these disorders.